We are studying metabolic changes which occur as an individual develops from a fetus to a mature adult. We are currently focusing on two areas: 1) monthly gonadotropin cycles in premenarchial girls and pubescent boys utilizing radioimmunoassay methods for measuring urinary luteinizing hormone and urinary follicle stimulating hormone and analyzing the data with autoregressive computer techniques, and 2) mineral metabolism in the rat, monkey fetus, and human newborn. Calcium kinetics are studied in the patients using stable calcium isotopes analyzed in the laboratory by mass spectrometry. Physiological effects of calcium are studied by measurements of ionized calcium in the blood. Trace element (zinc, copper and iron) analyses are performed by atomic absorption spectrophotomet as part of our studies of nutritional aspects of mineral metabolism in infancy and childhood.